Suppose I say that there's a fire in my room, and then you ask me why I believe there's a fire in my room. I could give a causal explanation for my belief (e.g. 'Some light bounced off a fire and this hit my eyes causing such-and-such brain changes in me) or I could try to justify the claim (e.g.'I seem to see a fire, and I don't tend to hallucinate').
These are two very different things! Thus, I think it's totally wrong to assume that the (potentially infinite series of) other beliefs I might express if asked to justify my claim that there's a fire in my room, somehow figured in causing the belief. If anything, these extra beliefs are probably simultanious results of a common cause, namely the fire.
Light hits my retina
I believe there's a fire.
I believe that I seem to see a fire.
I believe that I seem to seem to see a fire.
This is not to deny that beliefs CAN cause beliefs though, as in the case of conscious, Sherlock-Holmes-style chains of inference. Also the absence of certain beliefs might be necessary for the production of other beliefs (e.g. the absence of the belief that I have taken fire-hallucination causing drugs, might be required for causal stimulation by light from a fire to cause me to form the belief that there's a fire)